/*
    This file is part of Konsole, an X terminal.

    SPDX-FileCopyrightText: 2007-2008 Robert Knight <robertknight@gmail.com>
    SPDX-FileCopyrightText: 1997, 1998 Lars Doelle <lars.doelle@on-line.de>

    SPDX-License-Identifier: GPL-2.0-or-later

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA.
*/

#ifndef EMULATION_H
#define EMULATION_H

// System
#include <cstdio>

// Qt
#include <QKeyEvent>
// #include <QPointer>
#include <QTextCodec>
#include <QTextStream>
#include <QTimer>

// std
#include <memory>

#include "KeyboardTranslator.h"

namespace Konsole
{

class HistoryType;
class Screen;
class ScreenWindow;
class TerminalCharacterDecoder;

/**
 * This enum describes the available states which
 * the terminal emulation may be set to.
 *
 * These are the values used by Emulation::stateChanged()
 */
enum {
    /** The emulation is currently receiving user input. */
    NOTIFYNORMAL = 0,
    /**
     * The terminal program has triggered a bell event
     * to get the user's attention.
     */
    NOTIFYBELL = 1,
    /**
     * The emulation is currently receiving data from its
     * terminal input.
     */
    NOTIFYACTIVITY = 2,

    // unused here?
    NOTIFYSILENCE = 3
};

/**
 * Base class for terminal emulation back-ends.
 *
 * The back-end is responsible for decoding an incoming character stream and
 * producing an output image of characters.
 *
 * When input from the terminal is received, the receiveData() slot should be called with
 * the data which has arrived.  The emulation will process the data and update the
 * screen image accordingly.  The codec used to decode the incoming character stream
 * into the unicode characters used internally can be specified using setCodec()
 *
 * The size of the screen image can be specified by calling setImageSize() with the
 * desired number of lines and columns.  When new lines are added, old content
 * is moved into a history store, which can be set by calling setHistory().
 *
 * The screen image can be accessed by creating a ScreenWindow onto this emulation
 * by calling createWindow().  Screen windows provide access to a section of the
 * output.  Each screen window covers the same number of lines and columns as the
 * image size returned by imageSize().  The screen window can be moved up and down
 * and provides transparent access to both the current on-screen image and the
 * previous output.  The screen windows Q_EMIT an outputChanged signal
 * when the section of the image they are looking at changes.
 * Graphical views can then render the contents of a screen window, listening for notifications
 * of output changes from the screen window which they are associated with and updating
 * accordingly.
 *
 * The emulation also is also responsible for converting input from the connected views such
 * as keypresses and mouse activity into a character string which can be sent
 * to the terminal program.  Key presses can be processed by calling the sendKeyEvent() slot,
 * while mouse events can be processed using the sendMouseEvent() slot.  When the character
 * stream has been produced, the emulation will Q_EMIT a sendData() signal with a pointer
 * to the character buffer.  This data should be fed to the standard input of the terminal
 * process.  The translation of key presses into an output character stream is performed
 * using a lookup in a set of key bindings which map key sequences to output
 * character sequences.  The name of the key bindings set used can be specified using
 * setKeyBindings()
 *
 * The emulation maintains certain state information which changes depending on the
 * input received.  The emulation can be reset back to its starting state by calling
 * reset().
 *
 * The emulation also maintains an activity state, which specifies whether
 * terminal is currently active ( when data is received ), normal
 * ( when the terminal is idle or receiving user input ) or trying
 * to alert the user ( also known as a "Bell" event ).  The stateSet() signal
 * is emitted whenever the activity state is set.  This can be used to determine
 * how long the emulation has been active/idle for and also respond to
 * a 'bell' event in different ways.
 */
class Emulation : public QObject
{
    Q_OBJECT

public:
    /**
     * This enum describes the available shapes for the keyboard cursor.
     * See setKeyboardCursorShape()
     */
    enum class KeyboardCursorShape {
        /** A rectangular block which covers the entire area of the cursor character. */
        BlockCursor = 0,
        /**
         * A single flat line which occupies the space at the bottom of the cursor
         * character's area.
         */
        UnderlineCursor = 1,
        /**
         * An cursor shaped like the capital letter 'I', similar to the IBeam
         * cursor used in Qt/KDE text editors.
         */
        IBeamCursor = 2
    };

    /** Constructs a new terminal emulation */
    Emulation();
    ~Emulation() override;

    /**
     * Creates a new window onto the output from this emulation.  The contents
     * of the window are then rendered by views which are set to use this window using the
     * TerminalDisplay::setScreenWindow() method.
     */
    ScreenWindow *createWindow();

    /** Returns the size of the screen image which the emulation produces */
    QSize imageSize() const;

    /**
     * Returns the total number of lines, including those stored in the history.
     */
    int lineCount() const;

    /**
     * Sets the history store used by this emulation.  When new lines
     * are added to the output, older lines at the top of the screen are transferred to a history
     * store.
     *
     * The number of lines which are kept and the storage location depend on the
     * type of store.
     */
    void setHistory(const HistoryType &);
    /** Returns the history store used by this emulation.  See setHistory() */
    const HistoryType &history() const;
    /** Clears the history scroll. */
    void clearHistory();

    /**
     * Copies the output history from @p startLine to @p endLine
     * into @p stream, using @p decoder to convert the terminal
     * characters into text.
     *
     * @param decoder A decoder which converts lines of terminal characters with
     * appearance attributes into output text.  PlainTextDecoder is the most commonly
     * used decoder.
     * @param startLine Index of first line to copy
     * @param endLine Index of last line to copy
     */
    virtual void writeToStream(TerminalCharacterDecoder *decoder, int startLine, int endLine);

    /**
     * Copies the complete output history into @p stream, using @p decoder to convert
     * the terminal characters into text.
     *
     * @param decoder A decoder which converts lines of terminal characters with
     * appearance attributes into output text.  PlainTextDecoder is the most commonly
     * used decoder.
     */
    virtual void writeToStream(TerminalCharacterDecoder *decoder);

    /** Returns the codec used to decode incoming characters.  See setCodec() */
    const QTextCodec *codec() const
    {
        return _codec;
    }
    /** Sets the codec used to decode incoming characters.  */
    void setCodec(const QTextCodec *);

    /**
     * Convenience method.
     * Returns true if the current codec used to decode incoming
     * characters is UTF-8
     */
    bool utf8() const
    {
        Q_ASSERT(_codec);
        return _codec->mibEnum() == 106;
    }

    /** TODO Document me */
    virtual char eraseChar() const;

    /**
     * Sets the key bindings used to key events
     * ( received through sendKeyEvent() ) into character
     * streams to send to the terminal.
     */
    void setKeyBindings(const QString &name);
    /**
     * Returns the name of the emulation's current key bindings.
     * See setKeyBindings()
     */
    QString keyBindings() const;

    /**
     * Copies the current image into the history and clears the screen.
     */
    virtual void clearEntireScreen() = 0;

    /** Resets the state of the terminal. */
    virtual void reset() = 0;

    /**
     * Returns true if the active terminal program wants
     * mouse input events.
     *
     * The programUsesMouseChanged() signal is emitted when this
     * changes.
     */
    bool programUsesMouse() const;

    bool programBracketedPasteMode() const;

public Q_SLOTS:

    /** Change the size of the emulation's image */
    virtual void setImageSize(int lines, int columns);

    /**
     * Interprets a sequence of characters and sends the result to the terminal.
     * This is equivalent to calling sendKeyEvent() for each character in @p text in succession.
     */
    virtual void sendText(const QString &text) = 0;

    /**
     * Interprets a key press event and emits the sendData() signal with
     * the resulting character stream.
     */
    virtual void sendKeyEvent(QKeyEvent *, bool fromPaste);

    /**
     * Converts information about a mouse event into an xterm-compatible escape
     * sequence and emits the character sequence via sendData()
     */
    virtual void sendMouseEvent(int buttons, int column, int line, int eventType);

    /**
     * Sends a string of characters to the foreground terminal process.
     *
     * @param string The characters to send.
     * @param length Length of @p string or if set to a negative value, @p string will
     * be treated as a null-terminated string and its length will be determined automatically.
     */
    virtual void sendString(const char *string, int length = -1) = 0;

    /**
     * Processes an incoming stream of characters.  receiveData() decodes the incoming
     * character buffer using the current codec(), and then calls receiveChar() for
     * each unicode character in the resulting buffer.
     *
     * receiveData() also starts a timer which causes the outputChanged() signal
     * to be emitted when it expires.  The timer allows multiple updates in quick
     * succession to be buffered into a single outputChanged() signal emission.
     *
     * @param buffer A string of characters received from the terminal program.
     * @param len The length of @p buffer
     */
    void receiveData(const char *buffer, int len);

Q_SIGNALS:

    /**
     * Emitted when a buffer of data is ready to send to the
     * standard input of the terminal.
     *
     * @param data The buffer of data ready to be sent
     * @param len The length of @p data in bytes
     */
    void sendData(const char *data, int len);

    /**
     * Requests that the pty used by the terminal process
     * be set to UTF 8 mode.
     *
     * TODO: More documentation
     */
    void useUtf8Request(bool);

    /**
     * Emitted when the activity state of the emulation is set.
     *
     * @param state The new activity state, one of NOTIFYNORMAL, NOTIFYACTIVITY
     * or NOTIFYBELL
     */
    void stateSet(int state);

    /** TODO Document me */
    void zmodemDetected();

    /**
     * Requests that the color of the text used
     * to represent the tabs associated with this
     * emulation be changed.  This is a Konsole-specific
     * extension from pre-KDE 4 times.
     *
     * TODO: Document how the parameter works.
     */
    void changeTabTextColorRequest(int color);

    /**
     * This is emitted when the program running in the shell indicates whether or
     * not it is interested in mouse events.
     *
     * @param usesMouse This will be true if the program wants to be informed about
     * mouse events or false otherwise.
     */
    void programUsesMouseChanged(bool usesMouse);

    void programBracketedPasteModeChanged(bool bracketedPasteMode);

    /**
     * Emitted when the contents of the screen image change.
     * The emulation buffers the updates from successive image changes,
     * and only emits outputChanged() at sensible intervals when
     * there is a lot of terminal activity.
     *
     * Normally there is no need for objects other than the screen windows
     * created with createWindow() to listen for this signal.
     *
     * ScreenWindow objects created using createWindow() will Q_EMIT their
     * own outputChanged() signal in response to this signal.
     */
    void outputChanged();

    /**
     * Emitted when the program running in the terminal wishes to update the
     * session's title.  This also allows terminal programs to customize other
     * aspects of the terminal emulation display.
     *
     * This signal is emitted when the escape sequence "\033]ARG;VALUE\007"
     * is received in the input string, where ARG is a number specifying what
     * should change and VALUE is a string specifying the new value.
     *
     * TODO:  The name of this method is not very accurate since this method
     * is used to perform a whole range of tasks besides just setting
     * the user-title of the session.
     *
     * @param title Specifies what to change.
     * <ul>
     * <li>0 - Set window icon text and session title to @p newTitle</li>
     * <li>1 - Set window icon text to @p newTitle</li>
     * <li>2 - Set session title to @p newTitle</li>
     * <li>11 - Set the session's default background color to @p newTitle,
     *         where @p newTitle can be an HTML-style string ("#RRGGBB") or a named
     *         color (eg 'red', 'blue').
     *         See http://doc.trolltech.com/4.2/qcolor.html#setNamedColor for more
     *         details.
     * </li>
     * <li>31 - Supposedly treats @p newTitle as a URL and opens it (NOT IMPLEMENTED)</li>
     * <li>32 - Sets the icon associated with the session.  @p newTitle is the name
     *    of the icon to use, which can be the name of any icon in the current KDE icon
     *    theme (eg: 'konsole', 'kate', 'folder_home')</li>
     * </ul>
     * @param newTitle Specifies the new title
     */

    void titleChanged(int title, const QString &newTitle);

    /**
     * Emitted when the program running in the terminal changes the
     * screen size.
     */
    void imageSizeChanged(int lineCount, int columnCount);

    /**
     * Emitted when the setImageSize() is called on this emulation for
     * the first time.
     */
    void imageSizeInitialized();

    /**
     * Emitted after receiving the escape sequence which asks to change
     * the terminal emulator's size
     */
    void imageResizeRequest(const QSize &sizz);

    /**
     * Emitted when the terminal program requests to change various properties
     * of the terminal display.
     *
     * A profile change command occurs when a special escape sequence, followed
     * by a string containing a series of name and value pairs is received.
     * This string can be parsed using a ProfileCommandParser instance.
     *
     * @param text A string expected to contain a series of key and value pairs in
     * the form:  name=value;name2=value2 ...
     */
    void profileChangeCommandReceived(const QString &text);

    /**
     * Emitted when a flow control key combination ( Ctrl+S or Ctrl+Q ) is pressed.
     * @param suspendKeyPressed True if Ctrl+S was pressed to suspend output or Ctrl+Q to
     * resume output.
     */
    void flowControlKeyPressed(bool suspendKeyPressed);

    /**
     * Emitted when the cursor shape or its blinking state is changed via
     * DECSCUSR sequences.
     *
     * @param cursorShape One of 3 possible values in KeyboardCursorShape enum
     * @param blinkingCursorEnabled Whether to enable blinking or not
     */
    void cursorChanged(KeyboardCursorShape cursorShape, bool blinkingCursorEnabled);

    void handleCommandFromKeyboard(KeyboardTranslator::Command command);
    void outputFromKeypressEvent(void);

protected:
    virtual void setMode(int mode) = 0;
    virtual void resetMode(int mode) = 0;

    /**
     * Processes an incoming character.  See receiveData()
     * @p ch A unicode character code.
     */
    virtual void receiveChar(QChar ch);

    /**
     * Sets the active screen.  The terminal has two screens, primary and alternate.
     * The primary screen is used by default.  When certain interactive programs such
     * as Vim are run, they trigger a switch to the alternate screen.
     *
     * @param index 0 to switch to the primary screen, or 1 to switch to the alternate screen
     */
    void setScreen(int index);

    enum EmulationCodec { LocaleCodec = 0, Utf8Codec = 1 };
    void setCodec(EmulationCodec codec); // codec number, 0 = locale, 1=utf8

    std::vector<std::unique_ptr<ScreenWindow>> _windows;

    Screen *_currentScreen; // pointer to the screen which is currently active,
                            // this is one of the elements in the screen[] array

    std::unique_ptr<Screen> _primaryScreen; // 0 = primary screen ( used by most programs, including the shell
                                            //                      scrollbars are enabled in this mode )
    std::unique_ptr<Screen> _alternateScreen; // 1 = alternate      ( used by vi , emacs etc.
                                              //                      scrollbars are not enabled in this mode )

    // decodes an incoming C-style character stream into a unicode QString using
    // the current text codec.  (this allows for rendering of non-ASCII characters in text files etc.)
    const QTextCodec *_codec;
    std::unique_ptr<QTextDecoder> _decoder;
    const KeyboardTranslator *_keyTranslator; // the keyboard layout

protected Q_SLOTS:
    /**
     * Schedules an update of attached views.
     * Repeated calls to bufferedUpdate() in close succession will result in only a single update,
     * much like the Qt buffered update of widgets.
     */
    void bufferedUpdate();

private Q_SLOTS:

    // triggered by timer, causes the emulation to send an updated screen image to each
    // view
    void showBulk();

    void usesMouseChanged(bool usesMouse);

    void bracketedPasteModeChanged(bool bracketedPasteMode);

private:
    bool _usesMouse;
    bool _bracketedPasteMode;
    QTimer _bulkTimer1;
    QTimer _bulkTimer2;
};

}

#endif // ifndef EMULATION_H
